Explosion at NuStar energy facility in Northern California caught on camera

CROCKETT, Calif. -- As a fire raged at NuStar energy facility in Crockett, California, on Tuesday afternoon, an explosion that sent the top of a tank flying was caught on camera.

A witness shared a clip that shows a massive fireball created by the explosive chemicals. The roof of that container was sent flying in the air and floating back to the earth.

The fire prompted a hazardous materials emergency that led authorities to order about 12,000 people in two communities to stay inside with all windows and doors closed.

VIDEO: Massive flames, smoke rise from NuStar Energy facility fire in Crockett near Rodeo

Emergency sirens blared and thick plumes of black smoke and flames filled the skyline around the facility in Contra Costa County.

"This is a very dynamic, rapidly evolving situation,'' Capt. George Laing of the Contra Costa Fire Department said. He said authorities received numerous reports of explosions before the fire and that the flaming tanks "are releasing chemicals that are still burning."

The Associated Press contributed to this report.